Isolates from the Fusarium fujikuroi species complex, mainly F. sacchari, have been reported to be the causal agents of pokkah boeng in sugarcane in Brazil. However, inadequate information was ...available on the occurrence and genetic diversity of F. sacchari in Northeast Brazil, which is a limiting factor on management. Thus, isolates of F. subglutinans sensu lato from sugarcane plants with symptoms of pokkah boeng were evaluated using the sexual cross‐fertility to determine species. All the isolates produced black perithecia when they were crossed with the test isolates of F. sacchari. Three weeks after the crossing, the formation of fertile ascospores cirri was observed. Thirty‐four isolates were self‐sterile hermaphrodites, while 21 were fertile only as males. Five isolates were homothallic. The effective size Ne(f) of the population as a function of the frequency of hermaphrodites and female sterile strains was 95.5%. The F. sacchari isolates were separated into four genetic groups independent of geographic location. The mean of polymorphism among all populations was 79%, and the average unbiased genetic diversity (uh) was considered moderate (0.31). This study in addition to confirming that F. sacchari as the main species associated with pokkah boeng in sugarcane in Northeast Brazil, reveals the relationship of mating type and genetic diversity of F. sacchari. The unrestricted gene flow between regions is probably the best explanation for the low geographic correlation. This knowledge will help in the adoption of management measures with fungicides or resistant cultivars.
A high frequency of plants showing symptoms of wilting and root rot has been observed in tomato‐producing areas in Santarém and Belterra, Pará, Brazil. These plants showed symptoms ranging from ...yellowing to wilting, with roots displaying reduced development and darkening of the xylem. Four fungal isolates, derived from a collection of 12 obtained from symptomatic plants, were chosen for identification using both morphological and phylogenetic species concepts. To determine the identity of the fungi, DNA was extracted and used in PCR reactions. PCR products were sequenced from the TEF‐1α and RBP2 regions and compared with sequences in GenBank using BLASTn. Based on the phylogenetic analyses, the isolates were identified as Fusarium falciforme and Fusarium suttonianum, belonging to the species complex Fusarium solani – (FSSC), and Fusarium triseptatum, belonging to the species complex Fusarium oxysporum – (FOSC). The fourth isolate, COUFPI 295, grouped within a clade of F. kalimantanense and F. sangayamense from FOSC. The fulfilment of Koch's postulates confirmed that all isolates induced symptoms of root rot and concomitant reduction in root mass, leading to observable wilting symptoms. This is the first report of F. suttonianum, F. falciforme and F. triseptatum causing root rot and wilt in tomato plants in Brazil.
Cacao (Theobroma cacoa L.) is an important tropical fruit tree used in chocolate production. Among the biotic problems interfering with fruit production, phytopathogenic fungi stand out. During a ...visit to cocoa production areas in the municipality of Medicilândia, Pará, Brazil (Amazon region), we observed cocoa fruits with dark lesions and greyish‐white cottony mycelia growth. In order to determine the aetiological agent's identity, we extracted DNA and amplified part of the TEF‐1α and RBP2 genes and compared them with sequences in GenBank using the BLASTn tool. Based on molecular results and phylogenetic analysis, the isolates were identified as Calonectria hawksworthii. Inoculations in cacao fruits showed symptoms after 6 days and were similar to those collected in the field, confirming the postulates. This study is the first report of Ca. hawksworthii causing cocoa bean rot worldwide.
Fusarium verticillioides
is an important plant pathogen causing infections on ears and/or stalks of maize. This study aimed to compare sexual reproduction parameters in populations of
F. ...verticillioides
from distinct regions in the different Brazilian climatic zones where maize is grown. Fertility and effective population size were calculated from data generated by crossing field isolates with female fertile testers. Three hundred fungi isolates were obtained from maize kernels with Fusarium ear rot symptoms in different geographic regions of Brazil in the years 2012 and 2013. For the entire population, 231 out of 300 isolates were cross-fertile with tester isolates.
MAT1–1
and
MAT1–2
idiomorphs of the fertile isolates segregated in a 105:126 ratio. Female isolates (hermaphrodites) accounted for 96 out of 231 fertile isolates, while 135 were male-only isolates. The ratio of mating types within the population
N
e
(
mt
) was 99% of the count for the Brazilian population when the mating type idiomorphs were used as predictors to estimate the population size. However, when this calculation was made on the basis of the female fertile isolates, the
N
e
(
f
) was 83%. When the total population was divided by geographical/climatic regions, the frequencies of female fertile isolates were 33 out of 80 fertile isolates from the Northeast (equatorial tropical climate); 49 out of 73 fertile isolates from the Central-West (tropical climate); and only 14 out of 78 fertile isolates from the South (temperate climate), indicating that the sexual reproduction in
F. verticillioides
is likely favored by a tropical climate in Brazil. Brazilian populations of
F. verticillioides
show high fertility and high effective population size, suggesting the possibility of frequent sexual reproduction in the field, especially in populations from Tropical Climate regions of Brazil.
Plants of the genus Spondias are commonly cultivated in northern and north‐eastern Brazil for fruit production. Severe leaf anthracnose, caused by Colletotrichum spp., is frequently observed in ...several species of Spondias. The objectives of this study were to identify and characterize Colletotrichum species associated with anthracnose in species of Spondias by using the concept of morphological and phylogenetic analyses. Leaves with symptoms of anthracnose were collected from orchards in the state of Piauí, Brazil. Morphological identification; sequencing analysis of ACT, ITS and GS gene regions; and a pathogenicity test confirmed three Colletotrichum spp. (C. dianesei, C. siamense and C. brevisporum) were able to cause the disease. This is the first record of these species of Colletotrichum causing anthracnose in Spondias spp. in Brazil.
RESUMO Considerada uma das principais doenças do eucalipto, a ferrugem (Austropuccinia psidii) pode ocasionar sérios danos à cultura caso estratégias adequadas de manejo não sejam implantadas. De ...modo geral tem-se monocultura de eucalipto, com implicações epidemiológicas importantes. O objetivo desse estudo foi comparar o progresso da ferrugem do eucalipto consorciado com diferentes espécies em sistema agroflorestal, sob condições naturais de infecção. O experimento foi composto por três tratamentos (consórcios), dispostos de forma completamente aleatorizada no espaço. Em cada tratamento o eucalipto foi plantado com duas espécies diferentes, a saber: T1 - Cedro Australiano (Toona ciliata) + Eucalipto (Eucalyptus urograndis) + Banana (Musa acuminata); T2 - consórcio Amora (Morus celtidifolia) + Eucalipto + Pupunha (Bactris gasipaes), e T3 - Mogno Africano (Khaya ivorensis) + Eucalipto + Banana. Cada tratamento foi composto por seis repetições, totalizando 18 parcelas de 9m2 cada (2m x 4,5m), dispostos em linhas/aleia. Foram avaliadas altura, diâmetro da planta, incidência e severidade da doença, quinzenalmente. Os dados foram coletados em dois momentos distintos: pré-poda, compreendido de 17/08/2018 à 09/01/2019, e pós-poda, realizado de 17/04/2019 à 13/08/2019. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey (p<0,05). Verificou-se que o eucalipto apresentou maior desenvolvimento (altura e diâmetro) e menor intensidade da doença (incidência e severidade) no tratamento T2. Com base nos resultados, conclui-se que o plantio de eucalipto em consórcio com as espécies Amora + Eucalipto + Pupunha proporcionou menor intensidade da ferrugem e maior desenvolvimento das plantas.
ABSTRACT Fava bean is one of the major domesticated and the second most cultivated species of the genus Phaseolus. Anthracnose caused by Colletotrichum truncatum affects fava bean in several stages of its development, constituting an important disease for the crop; however, only few studies confirm genotypes as source of resistance. Thus, the present study aimed to select fava bean accessions resistant to C. truncatum and to verify whether there are morpho-agronomic traits associated with resistance source through track analysis. Twenty-two accessions of Phaseolus lunatus were evaluated for their resistance to C. truncatum and were morphologically and agronomically characterized in a distinct experiment. Resistance was evaluated by visual analysis, as well as by lesion measurement with Asses 2.0 program. The morpho-agronomic characterization of the accessions was performed based on fourteen quantitative descriptors. The obtained data were jointly analyzed by track analysis in order to identify related descriptors regarding resistance to anthracnose. The genotypes UFPI 842 and UFPI 832 were confirmed as sources of high resistance to the fungus C. truncatum and presented greater averages of bean pod width. Therefore, the positive direct effect of pod width on the infection level indicates that simultaneous benefits can be obtained through a combined selection of these traits. The present results will be useful to the fava bean breeding program for allowing the development of resistant C. truncatum cultivars with excellent agronomic characteristics.
ABSTRACT The fungal genus Curvularia is associated with a number of diseases in plants, commonly producing foliar spots in forage grasses. The objective of this study was to characterize the ...morphological and molecular diversity of the isolates of Curvularia sp. associated with Andropogon seeds, and to assess both their capacity to transmit disease and the pathogenicity of this fungus to crop. Ten isolates of Curvularia sp. were sourced from Andropogon seeds from agricultural producing regions in the Brazilian states Tocantins and Pará. Morphological characterization was achieved by observing fungus colonies and conidia and molecular characterization by DNA extraction and amplification with sequence-specific primers. The disease transmission was evaluated from seed sowing, in which after 40 days typical symptoms of Curvularia sp. were observed. Pathogenicity was evaluated by inoculating conidial suspension into the leaves of healthy plants, and after ten days, inspecting for pathogenic symptoms. Based on morphological and molecular features, the pathogen associated with Andropogon seeds was identified as Curvularia lunata, which, as such, is transmitted through the Andropogon plants via its seeds and is pathogenic to this species of forage grass.
Fusarium udum
is the causal agent of a wilt disease on pigeon pea (
Cajanus cajan
) in tropical regions. This species shares morphological characteristics with
F. oxysporum
, leading to ...misidentification when the diagnosis is solely based on morphological markers. The sexual stage of this fungus was observed on stems of
Cajanus
in India and was formally described as
Gibberella indica
. In Brazil, a wilt disease is reported on
Crotalaria
, but the etiological agent has not been identified correctly so far. In this study, we tested the hypothesis that the causal agent of a wilt on
Crotalaria
belongs to the same species pathogenic to
C. cajan
. Strains obtained from diseased
Crotalaria
spp. were characterized through molecular phylogeny of
TEF
,
TUB
and
RPB2
, laboratory crosses, morphological markers, and pathogenicity tests. Strains from
Crotalaria
from Brazil formed a well-supported clade with
F. udum
strains from
Crotalaria
and
Cajanus
from other countries. Strains from Brazil intercrossed among themselves and also with others from all geographic regions, and formed fertile perithecia, defining a distinct mating population inside the
Fusarium fujikuroi
species complex. One strain obtained from
Cajanus cajan
in India is indicated as epitype, and female-fertile tester strains of both mating types were selected for the identification of field isolates through sexual crosses. These results confirm that the species associated with wilt disease on
Crotalaria
and
Cajanus
is
F. udum
. Wilt symptoms caused by
F. udum
in
Cr. ochroleuca
are described and illustrated.
ABSTRACT The fungi Colletotrichum truncatum and Macrophomina phaseolina are among the main pathogens associated with lima bean seeds in Brazil, and they are the causal agents of anthracnose and ...charcoal rot, respectively. The aim of this study was to verify the seed-seedling transmission of C. truncatum and M. phaseolina in artificially inoculated lima bean seeds. Potato-dextrose-agar (PDA) media with different hydric potentials were obtained after the addition of mannitol. Isolates of C. truncatum and M. phaseolina were peaked to these media. Forty grams of seeds were distributed over the fungal mycelium, remaining there for different exposure periods, as a function of each treatment: T1: 0.0 MPa without inoculum for 48 h; T2: 0.0 MPa for 48 h; T3: -0.2 MPa for 48 h; T4: -0.4 MPa for 48 h; T5: -0.6 MPa for 72 h; T6: -0.8 MPa for 96 h and T7: -1.0 MPa for 120 h. The seeds were incubated at 25 ºC under a 12-hour photoperiod. Germination in a paper roll, emergence of seedlings in sand and seed health in PDA were evaluated. T4 provided the best conditions to temporarily prevent seed germination, promoting a greater incidence of seeds infected by C. truncatum and a greater percentage of diseased plants. M. phaseolina reduced seed germination, independently of the inoculated treatment. Both fungi were transmitted from the seeds to the seedlings of lima bean, causing symptoms in various aerial parts. C. truncatum and M. phaseolina transmission rate was 83.1% and 76.46%, respectively.
RESUMO Os fungos Colletotrichum truncatum e Macrophomina phaseolina estão entre os principais patógenos associados a sementes de feijão-fava no Brasil, sendo os agentes causais da antracnose e da podridão de carvão, respectivamente. Este trabalho teve como objetivo verificar a transmissão semente-plântula de C. truncatum e M. phaseolina em sementes de feijão-fava inoculadas artificialmente. Meios de cultura batata-dextrose-agar (BDA) com diferentes potenciais hídricos foram obtidos após a adição de manitol. Isolados de C. truncatum e M. phaseolina foram repicados para esses meios. Quarenta gramas de sementes foram distribuídas sobre o micélio fúngico, permanecendo por diferentes períodos de exposição, em função do tratamento: T1: 0,0 MPa sem inóculo por 48 h; T2: 0,0 MPa por 48 h; T3: - 0,2 MPa por 48 h; T4: -0,4 MPa por 48 h; T5: -0,6 MPa por 72 h; T6: - 0,8 MPa por 96 h e T7: -1,0 MPa por 120 h. As sementes foram incubadas a 25 ºC, com fotoperíodo de 12 horas. Foram avaliadas a germinação em rolo de papel, a emergência de plântulas em areia e a sanidade de sementes em BDA. O T4 proporcionou melhores condições para impedir temporariamente a germinação das sementes, promovendo maior incidência de sementes infectadas por C. truncatum e maior porcentagem de plântulas doentes. M. phaseolina reduziu a germinação das sementes, independente do tratamento inoculado. Ambos os fungos foram transmitidos das sementes para as plântulas de feijão-fava, causando sintomas em diferentes órgãos aéreos. A taxa de transmissão de C. truncatum e M. phaseolina foi de 83,1% e 76.46%, respectivamente.
Sugarcane pineapple rot is an important sugarcane stem disease that also affects germination and sprouting. In Brazil, the disease is caused by
Thielaviopsis paradoxa sensu
lato which has been split ...into at least five distinctive phylogenetic and biological species in the reinstated genus
Thielaviopsis
. In this study, three purported strains of
T. paradoxa
s. lat. isolated from sugarcane stems were characterized and compared with a strain from pineapple fruit, using morphology, DNA sequence analyses and sexual compatibility tests. Inoculations were also performed on asymptomatic stems of plants to assess the pathogenicity of the four fungal strains on sugarcane. Based on results of the phylogenetic analyses of combined ITS and TEF-1a gene sequences, the strains were identified as
T. ethacetica
. This was also supported by sexual compatibility tests, as crossings between the pineapple strain and some sugarcane strains resulted in the formation of perithecia exuding ascospore masses at their apices. The inoculation test on sugarcane resulted in stem rot and in reduced germination of buds.
Thielaviopsis ethacetica
is thus the species causing pineapple sett rot disease in Brazil.
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